Electrical resistance heating apparatus



March 28, 1967 H. E. PETERSON 3,311,734

ELECTRICAL RESISTANCE HEATING APPARATUS Original Filed Dec. 4. 1963 5 f 7 6 22 F fikkoMsrn? i-o g c 3 24 //VPU 7' w ,5. 212 722 5. c. R I AND L COMPARATfl/Q g 3] .32

fnz/erzz'a 7-! firierz zfei'erson UnitedStates Patent O 3,311,734 ELECTRICAL RESIS ANCE HEATING APPARATUS Herbert E. Peterson, 815 W. Northeast Shore Drive, McHenry, Ill. 60050 Continuation of abandoned application Ser. No. 328,017, Dec. 4, 1963. This application Apr. 11, 1966, Ser. No. 541,857

This application is a continuation of Serial No. 328,017 filed on Dec. 4, 1963, now abandoned.

This invention relates to an electrical resistance heating apparatus, and more particularly to a substantially simplified apparatus comprised of a minimum number of operating parts.

A variety of electrical resistance heating arrangements have been constructed to heat rods, wires, sheets, blanks, and various other metallic materials to facilitate working of the material. While adequate from the standpoint of providing the requisite heating to work the metal, such other arrangements have been relatively uneconomical to produce, complex, and difficult to operate. In contrast, the present invention eliminates many of the complex control elements, such as relays, tapped windings on inductive reactor units, and other complex structures, for example, those depicted in United States Patent 3,042,786.

In order to acquaint those skilled in the art with the best mode contemplated for making and utilizing the invention, a description thereof is set forth in connection with the accompanying drawing, in the several figures of which like reference numerals identify like elements, and in which:

FIGURE 1 is a simplified schematic diagram indicating the intercoupling of various components of the inventive combination; and

FIGURE 2 is a perspective illustration showing the invention in relation to other units.

As shown in FIGURE 1, a pair of input conductors 5 and 6 are provided to transfer AC. input energy from a commercial or other power source (not shown) to one side of on-off switch 7. Responsive to closure of switch 7, conductors 5 and 6 are connected to conductors 8 and 9, and conductor 8 is coupled to one end of primary winding 10 of step-down transformer 11. Conductors 8 and 9 are also coupled to the energy input connections of a power supply 12 which utilizes silicon controlled rectifiers (SCRs) to provide an output D.-C. signal on conductors 13 and 14 responsive to a D.-C. control signal received over conductors 15 and 16. Input conductor 9 is also coupled over main windings 17 and 18 of saturable reactor 19 to the other end of primary winding 10, and control winding 20 of this reactor is coupled to conductors 13 and 14 to receive the control or saturation level signal from power supply 12.

Secondary winding 21 of transformer 11 is coupled over conductors 22 and 23 to contacts 24 and 25, respectively. A load member 26 is shown disposed between and in contact with contacts 24 and 25. These contacts may be work holders, rotary supports, or other members which temporarily support load 26 as it passes between the contact pair 24, 25. The exact configuration and support of the contacts will depend upon the precise metal (load) to be worked, its shape, and the manner in which the metal should be held for suchworking.

A thermocouple 27 is disposed adjacent load member 26 to provide an electrical output signal over conductors 28 and 29, the level of which signal varies as a function of the value of temperature sensed by the thermocouple. This indication or electrical signal is transferred by conductors 28 and 29 to a pyrometer 30, wherein it is utilized to actuate a meter movement calibrated in the thermal units and thus provide a visible indication of the tempera- 3,311,734 Patented Mar. 28, 1967 ture of load 26. Conductors 28 and 29 also transfer the electrical signal to the input side of control setting and comparator unit 31, which includes a knob 32 or a similar adjustable means which facilitates setting the desired temperature at which metal 26 should be worked. Such comparator unit may include a simple arrangement such as a potentiometer with, a battery (neither of which is illustrated) to provide a reference voltage related to the desired temperature of the metal to be worked. In a wellknown manner, this reference voltage is compared against the signal voltage received from conductors 28 and 29 to provide a difference signal indicating the extent of deviation between the temperature desired and actual temperature of load 26. This difference signal is applied over conductors 15 and 16 to power supply 12, to regulate the time duration of the SCRs conduction during each complete cycle of application of the A.-C. input signal over conductors 8 and 9 to the SCR power supply. The

duration of SCR conduction regulates the level of the saturating signal applied over conductors 13 and 14 to control winding 20, thereby regulating the effective im pedance presented between primary winding 10 and conductors 8 and 9. Such regulation produces :1 corresponding regulation of the amount of energy transferred over transformer 21 to load 26. Accordingly, it is manifest that the circuit combination depicted in FIGURE 1 provides an accurate and simple means for setting the desired temperature (by adjusting knob 32), and includes a closed loop regulating system for continually correcting any deviation between the actual temperature of metal 26 and the desired temperature as set on knob 32 of the comparator.

Considering now the perspective showing of FIGURE 2, a portable heating apparatus 40 is depicted in the left hand portion of this drawing. In the right hand portion, a material processing apparatus 41 is illustrated. Apparatus 41 may include a first stand 42 on which the movable contact arrangement 24 is supported, and another stand 43 in which the particular drawing, swaging, or other metal deforming step is effected. Except for the indicated placement of contact set 24, all of the other circuit components illustrated in FIGURE 1 are supported in or upon heating apparatus 40.

Contact arrangement 25, shown supported directly on apparatus 40, includes an upper fixed contact 44 and a lower movable contact 4-5. A bias spring 46 is positioned between a stop member 47 and movable contact 45. Accordingly, a portion of wire or other metal 26 is readily inserted into contact set 25, and the other contact set 24 can likewise be made with a spring bias arrangement to facilitate the insertion of the metal stock to be worked. After insertion and energization of the equipment, the stock will travel the substantially linear path indicated in FIGURE 2.

Visible in the lower portion of heater apparatus 40 is the casing of transformer unit 11, from which insulated conductor 22 passes energy to contact set 24. The other energy transfer conductor 23, also insulated, passes energy from the other end of secondary winding 21 to contact arrangement 25.

It is emphasized that the only unit required for use with the metal processing apparatus 41 is the heater arrangement 40, which both provides the desired level of energization and acts as a support for contact set 25. Such operation is in marked contradistinction to prior art techniques, which generally include the mounting of a fixed contact support at a distance from the metal processing equipment 41. Accordingly, such known arrangements require that the heater be connected both to the support standard and to the apparatus 41. Utilization of the present invention obviates the expense and spatial requirements heretofore necessitated by positioning the fiXed contact post adjacent each metal working apparatus. At times heating of the metal to be worked at a given apparatus is not required, and thus one or a few of the portable heater-and-contact-support units 40 can adequately service a substantially larger number of metal working units.

In addition, with the currents of high level that pass through the heated portion of metal 26, it is desirable to maintain the conductors of the circuit as close together as possible, thereby minimizing the inductive reactance of the current loop. Moreover, by reducing the length of leads 22 and 23 as much as practicable, the resistance losses in the circuit are correspondingly reduced and the efficiency of the entire circuit arrangement is enhanced.

While only a particular embodiment of the invention has been described and illustrated, it is apparent that modifications and alterations may be made therein. It is, therefore, the intention in the appended claims to cover all such modifications and alterations as may fall within the true spirit and scope of the invention.

What is claimed is: I 1. In a system for regulating the amount of electrical energy transferred to a load to be heated by the energy, the combination of:

a step-down transformer having a primary winding and a secondary winding; saturable reactor means having a control winding for regulating the level of saturation and at least one output winding for passing electrical energy as a function of the specific saturation level of said reactor means; means, including said output winding of the saturable reactor means, for passing A.C. energy to the primary winding of the transformer; conductor means for passing electrical energy from the secondary Winding of the transformer to the load; sensing means disposed adjacent said load for sensing the temperature thereof and for producing a signal voltage related to the temperature of said load;

indicating means coupled to said sensing means for providing a visual indication of the load temperature;

power supply means for receiving A.C. energy, rectifying the AC. energy in proportion to a difference signal, and passing the resultant D.C. energy to said control winding of the saturable reactor means; and

comparator means, coupled to said sensing means, for receiving said signal voltage indicating the tempera ture of said load, and having an output circuit connected to apply said difference signal to said power supply and thus regulate the saturation level of the saturable reactor means, said comparator means including adjusting means for establishing a reference voltage for comparison with said signal voltage to provide said difference signal, to govern the desired saturation level of the saturable reactor means and thereby control the temperature of the load.

2. A system as claimed in claim 1 in which said conductor means for passing electrical energy from the secondary winding of the transformer to the load includes first and second electrical contact sets, with a stationary material processing apparatus on which said first electrical contact set is mounted, and a portable apparatus on which said second electrical contact set is mounted, including resilient means for urging a portion of said second contact set against the load to facilitate insertion and removal of the load from the system.

References Cited by the Examiner UNITED STATES PATENTS 1,991,248 2/1935 Hartigan 219-503 2,079,466 5/1937 Phillips 219'503 X 2,294,775 9/1942 Edwards et al. 219-503 X 3,042,786 7/1962 Babcock et a1 219-50 RICHARD M. WOOD, Primary Examiner. 

1. IN A SYSTEM FOR REGULATING THE AMOUNT OF ELECTRICAL ENERGY TRANSFERRED TO A LOAD TO BE HEATED BY THE ENERGY, THE COMBINATION OF: A STEP-DOWN TRANSFORMER HAVING A PRIMARY WINDING AND A SECONDARY WINDING; SATURABLE REACTOR MEANS HAVING A CONTROL WINDING FOR REGULATING THE LEVEL OF SATURATION AND AT LEAST ONE OUTPUT WINDING FOR PASSING ELECTRICAL ENERGY AS A FUNCTION OF THE SPECIFIC SATURATION LEVEL OF SAID REACTOR MEANS; MEANS, INCLUDING SAID OUTPUT WINDING OF THE SATURABLE REACTOR MEANS, FOR PASSING A.C. ENERGY TO THE PRIMARY WINDING OF THE TRANSFORMER; CONDUCTOR MEANS FOR PASSING ELECTRICAL ENERGY FROM THE SECONDARY WINDING OF THE TRANSFORMER TO THE LOAD; SENSING MEANS DISPOSED ADJACENT SAID LOAD FOR SENSING THE TEMPERATURE THEREOF AND FOR PRODUCING A SIGNAL VOLTAGE RELATED TO THE TEMPERATURE OF SAID LOAD; INDICATING MEANS COUPLED TO SAID SENSING MEANS FOR PROVIDING A VISUAL INDICATION OF THE LOAD TEMPERATURE; POWER SUPPLY MEANS FOR RECEIVING A.C. ENERGY, RECTIFYING THE A.C. ENERGY IN PROPORTION TO A DIFFERENCE SIGNAL, AND PASSING THE RESULTANT D.C. ENERGY TO SAID CONTROL WINDING OF THE SATURABLE REACTOR MEANS; AND COMPARATOR MEANS, COUPLED TO SAID SENSING MEANS, FOR RECEIVING SAID SIGNAL VOLTAGE INDICATING THE TEMPERATURE OF SAID LOAD, AND HAVING AN OUTPUT CIRCUIT CONNECTED TO APPLY SAID DIFFERENCE SIGNAL TO SAID POWER SUPPLY AND THUS REGULATE THE SATURATION LEVEL OF THE SATURABLE REACTOR MEANS, SAID COMPARATOR MEANS INCLUDING ADJUSTING MEANS FOR ESTABLISHING A REFERENCE VOLTAGE FOR COMPARISON WITH SAID SIGNAL VOLTAGE TO PROVIDE SAID DIFFERENCE SIGNAL, TO GOVERN THE DESIRED SATURATION LEVEL OF THE SATURABLE REACTOR MEANS AND THEREBY CONTROL THE TEMPERATURE OF THE LOAD. 